The present invention relates to an automatic gear shifting method for a motor vehicle installed with a manual gear box.
The manual gear boxes are advantageous over the automatic transmissions using a torque converter in their fuel economy because there is no power loss due to the slippage in the torque converter.
There have been many proposals as to automatic gear shifting method for the manual gear box transmission. A known automatic gear shifting method is graphically illustrated in FIG. 1.
Referring to FIG. 1, line a represents a clutch stroke, line b a throttle valve opening degree. As will be readily understood from this Figure, the closing movement of the throttle valve toward the closed position thereof and the clutch disengagement are initiated simultaneously at t.sub.1 before the subsequent step of initiating the clutch reengagement at t.sub.2 and the step of returning the throttle valve toward the initial opening degree at t.sub.3. Actual gear shifting is effected when the clutch has been disengaged.
The problem encountered with this prior art method is in that a drop in the output torque due to the clutch disengagement will become rapid under the vehicle operating condition with large throttle opening degrees, thus causing uncomfortable deceleration during shifting operation under this condition. The present invention aims at solving this problem.